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Abstract:

Improved methods and apparatus for cross-sectional scanning of parts
employ a scanning station in which the focal plane of the scanning
apparatus never moves in the vertical direction, i.e., the direction in
which the stage of the part/potting combination moves. Distinct steps of
material removal and scanning alternate with an intermediate step of
moving the part/potting combination in the vertical direction after a
surface layer has been removed, thus placing the newly-created surface
back into the non-moving focal plane for the next scanning step. A
removal station (not the stage carrying the part/potting combination)
repeatedly moves into and out of the field of view of the scanning
station between scanning steps. The material removal station is specially
configured to remove the desired surface layer of the part/potting
combination and the created debris, without requiring the separate
environment characteristic of previous commercial applications.

Claims:

1. A system for scanning a substantially transparent part having an outer
surface, comprising: a data gathering station, a material removal
station, and a table providing only vertical movement of the part
relative to the data gathering station along a vertical path; in which
the part is encased in a potting material to form an assembly; the
material removal station removing a portion of the assembly to expose a
surface.

2. The system of claim 1, in which the data gathering station comprises at
least one of: an image data acquisition device for successively acquiring
images of the part after removal of a predetermined contour; and an
electronic device operatively associated with the image data acquisition
device for receiving and storing the images.

3. The system of claim 1, in which the material removal station comprises
at least one of: a tool constructed and arranged to remove a
predetermined contour of material from the part; and a drive mechanism
constructed and arranged to provide relative horizontal movement between
the tool and the part.

4. The system of claim 1, in which the table holds the part and further
comprises a drive mechanism constructed and arranged to provide vertical
movement between the table and the data gathering station along the
vertical path.

5. A method for producing electronic data representations of an object
having a plurality of surfaces, the method comprising:encasing the object
within a preselected encasing material to form an encasement, such
encasing being done so that all surfaces of the object are coated with
the encasing material and so that the encasing material substantially
fills all interior volumes of the object;removing successively from the
encasement a plurality of layers of material, each layer of material
removed having predetermined dimensions of length, width and depth and a
predetermined geometric shape, so as to expose an encasement surface, and
assigning a value to each layer representative of its elevation within
the object;acquiring an electronic representation of selected exposed
encasement surfaces after a predetermined layer has been removed;
andprocessing each electronic representation to create a predetermined
electronic representation of each the encasement surface.

6. The method of claim 5, in which the selected electronic representation
is a solid model of the object and in which the processing step includes
converting each electronic representation into a layered point cloud
representative of the object.

7. The method of claim 5, in which the method further comprises lofting a
surface onto each layered point cloud.

8. The method of claim 5, in which the method further comprises importing
each the layer into CAD space and stacking the layers according to their
assigned elevation value.

9. The method of claim 5, and further including creating a solid between
adjacent layers.

10. The method of claim 5, in which the selected electronic representation
is a solid model of the object.

11. The method of claim 5, in which the selected electronic representation
is a surface model of the object.

12. The method of claim 5, in which the contour removing step removes
contour of material such that successively exposed surfaces of the object
are substantially parallel to each other, the method further
including:identifying a feature of interest in the object; andorienting
the object such that the exposed surfaces of the object are non-parallel
to the feature of interest so that at least one exposed surface extends
through the feature of interest.

13. The method of claim 5, in which the acquiring step includes scanning
each encasement surface using a scanner to create a scanned image of each
encasement surface.

14. The method of claim 5, in which the selected electronic representation
is a surface model of the object and in which the processing step
includes convening each electronic representation into a line an drawing
defining the perimeter edges of the internal and external edges of the
object.

15. The method of claim 14, in which the processing step further includes
stacking the line art drawings and lofting a surface thereon.

16. The method of claim 14, in which the processing step further includes
converting the line art drawings into a vector data file.

17. The method of claim 16, in which the processing step further includes
importing the vector data file into 3D CAD space and lofting a surface
thereon.

18. The method of claim 5, in which the layers have upper and lower
surfaces and a substantially uniform thickness, the upper and lower
surfaces being substantially parallel to each other.

19. The method of claim 5, in which the electronic representation is a
raster planar image and in which the processing step further includes
importing the raster planar image into 3D CAD space and converting the
imported images into a solid model of the object.

20. The method of claim 5, in which the layers have upper and lower
surfaces being substantially parallel to each other and in which the
layers increase in thickness as successive layers of the encasement are
removed to form each the predetermined contour.

21. The method of claim 5, in which the layers have upper and lower
surfaces being substantially parallel to each other and in which the
layers decrease in thickness as successive layers of the encasement are
removed to form each the predetermined contour.

22. The method of claim 5, in which the predetermined contour has a
substantially uniform thickness.

23. Apparatus for producing electronic data representations of an object,
the object being formed from at least one material, the apparatus
comprising:a material removal station;a data gathering station having a
fixed position focal plane; anda stage movable in only a vertical
direction perpendicular to the fixed position focal plane;in which the
material removal station comprises:means for removing a predetermined
layer of material from the object;in which the data gathering station
comprises:means for successively imaging the object after removal of a
predetermined layer; andmeans for storing data gathered by the means for
imaging; andin which the stage comprises:a table for holding the
object;means for moving the table only in a single direction to maintain
the object in imaging alignment with the means for successively imaging
the object before and after the means for removing a predetermined layer
of material from the object moves into and out of position for removing a
layer of material; andmeans for moving the material removal station in a
second direction substantially perpendicular to the Z axis into and out
of relative material removing position in which it removes a
pre-determined layer of material.

24. The apparatus of claim 23, in which the data gathering station further
comprises means for manipulating data gathered by the imaging means and
stored in the data storage means to produce a three-dimensional drawing
of the object.

25. The apparatus of claim 23, in which the object is encased within an
encasing material to form an encasement and in which the layer removing
means removes a predetermined layer of the encasement.

26. The apparatus of claim 23, in which the means for removing a
predetermined layer of material comprises an end mill including at least
one flute, the end mill being rotated about an axis substantially
perpendicular to the axis of motion of the stage and substantially
parallel to the common plane, such that a planar surface of the object is
exposed by the removal of material by at least one flute as the end mill
is rotated.

27. The apparatus of claim 23, in which the removal of the predetermined
layer exposes an object surface and an encasing material surface and in
which the object surface contrasts with the encasing material surface so
that a line of demarcation may be determined between the surfaces.

28. The apparatus of claim 23, in which the predetermined layer is of
substantially uniform thickness.

29. The apparatus of claim 23, in which the data gathering station further
comprises means manipulating data gathered by the imaging and stored in
the data storage means to produce a three-dimensional drawing of the
object.

30. A method of scanning a part, comprising:(a) encasing the part into a
potting material to form an assembly;(b) while the assembly is not
moving, progressively horizontally removing a portion of the assembly to
expose a surface;(c) moving the surface substantially only vertically to
a position in a fixed position focal plane; and(d) scanning the surface.

31. The method of claim 30, further comprising repeating (b) and (c) after
(d).

Description:

BACKGROUND

[0001]Cross-sectional scanning of parts, and the processing of the data
generated in the same, is described in U.S. Pat. Nos. 5,139,338;
5,261,648; 5,880,961; 6,091,099; and 6,407,735. Such techniques, broadly
speaking, involve the repeated optical scanning of a part that has been
encased in a potting material so that, as successive layers of the
part/potting combination are removed, data regarding the dimensions of
the part are generated by a computer processing the scanned data of the
image of each successive surface remaining after the preceding layer is
removed. The optical contrast between the portions of the surface due to
the potting material and those due to the material of the part identifies
the dimensions of the part itself. Post-acquisition data processing
techniques improve the utility of the data for various purposes. One such
technique is described in U.S. Pat. No. 6,407,735.

SUMMARY

[0002]Commercial embodiments of the techniques and systems disclosed in
the patents listed above generally involve what may be called an "X-Axis"
approach, meaning that a stage or shuttle carries the part/potting
combination linerally back and forth along an axis between separate
scanning and material removal stations. This application discloses
various embodiments of improved methods and apparatus for cross-sectional
scanning of parts, utilizing a so-called "Z-Axis" approach. These
embodiments employ a scanning station in which the focal plane of the
scanning apparatus never moves in the vertical or Z direction, i.e., the
direction in which the stage of the part/potting combination moves. The
distinct steps of material removal and scanning alternate with an
intermediate step of moving the part/potting combination in the Z
direction after a surface layer has been removed, thus placing the
newly-created surface back into the focal plane for the next scanning
step. To accomplish this, a removal station (not the stage carrying the
part/potting combination) repeatedly moves in the +/-X direction, i.e.,
into and out of the field of view of the scanning station, between
scanning steps. The material removal station is specially configured to
remove the desired surface layer of the part/potting combination and the
created debris, without requiring the separate environment that
previously mandated the use of the X-Axis approach in commercial
applications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003]The figures illustrate a preferred embodiment and thus it should be
understood that minor changes in shape, proportion, size, and the like
are not critical to the scope of the disclosure except as specifically
noted elsewhere below.

[0004]FIG. 1 is a schematic side view of a system according to the
detailed description below.

[0005]FIG. 2 is a close-up upper perspective view of a prototype
embodiment of a portion of FIG. 1.

[0006]FIG. 3 is a close-up lower perspective view of a portion of FIG. 2.

DETAILED DESCRIPTION

[0007]In general terms, this application pertains to substantially
improved versions of the methods and apparatus for cross-sectional
scanning disclosed in U.S. Pat. Nos. 5,139,338; 5,261,648; 5,880,961; and
6,091,099. Each of these documents is incorporated by reference and
familiarity with the basic operating principles taught in each of these
documents is assumed in the following discussion. Thus, details known in
the art will be understood, such as those associated with the removal of
successive layers of the part/potting combination, generation of data
regarding the dimensions of the part (including the computer processing
of the scanned data of the image of each successive surface remaining
after the preceding layer is removed), and the post-acquisition data
processing techniques that improve the utility of the data for various
purposes.

[0008]Referring to FIGS. 1-3, a prototype cross-sectional scanner system
10 comprises vertically moving stage 11 and fixed-focal plane scanner 12.
In the preferred embodiment, scanner 12 is stationary with respect to
system 10 and thus only the vertical motion of stage 11 need be
considered explicitly. However, although it is not preferred, it is
possible for scanner 12 to move relative to stage 11, but the remainder
of this discussion assumes that only stage 11 moves in the vertical
direction with the understanding that the non-preferred approach is also
included. Stage 11 supports part/potting combination 13 so that vertical
motion of stage 11 advances combination 13 in the vertical direction
toward scanner 12. The initial motion places the upper surface of
combination 13 at a position corresponding to the height of one thickness
of material to be removed above the fixed location F of the focal plane
of scanner 12. Then such a thickness is removed from the upper
(scanner-facing) surface of combination 13 by cutting subsystem 14
described further below. This places the upper surface so created exactly
at the position of the fixed focal plane of scanner 12, and scanning
proceeds according to conventional techniques. A repeated series of
stepwise motions, each corresponding in distance to the thickness of
material to be removed, alternates with removal of such material followed
by scanning of the new upper surface created. Thus, each scanning step
occurs at the location of the fixed focal plane. The part/potting
combination never shuttles in the X or Y directions.

[0009]In general, scanner 12 is any multi-pixel scanner, camera, or
similar optical image capture device such as a CCD array, line scan
camera, or area scan camera. High resolution (155,000 pixels per square
centimeter or greater) (megapixel per square inch or greater) image
capture equipment is preferred for scanner 12. In this case, a preferred,
but not limiting, thickness of each slice is 25.4 micrometers [one
thousandth (0.001) inch]. This combination results in data points
measured at a scale that is 25.4 micrometers [one thousandth (0.001)
inch] in each of the three orthogonal primary directions.

[0010]References to thickness measurements should be understood as
referring to measurements taken normal to the surface of the part/potting
combination 13. The part itself typically is oriented at some
non-orthogonal angle within the potting material and thus distances
measured in the principal X, Y, and Z planes may expose amounts of the
part that are greater than or less than the thickness as measured normal
to the surface of the part at the location of measurement.

[0011]As shown, part/potting combination 13 is generally rectangular in
cross-section in each of the three principal directions. It is preferred,
but not required, that combination 13 have maximum dimensions on the
order of 44.4 millimeters by 63.5 millimeters by 88.9 millimeters (13/4
inch by 21/2 inch by 31/2 inch). This is only a preference.

[0012]Cutting subsystem 14 is, in general, any means for removing an
amount of the upper surface of the part/potting combination. In the
embodiment illustrated, it specifically includes a rotating single-end
center-cutting end mill supplied by Niagara Cutter of Amherst, N.Y. under
their model number A377 as designated by that manufacturer. This device
has three flutes in a right-hand orientation at a helix angle of
37° and dimensions (flute diameter by shank diameter by cut length
by overall length) of 9.5 millimeters by 9.5 millimeters by 38.1
millimeters by 82.6 millimeters (3/8 inch by 3/8 inch by 11/2 inches by
31/4 inches). The device may be uncoated or coated as available from the
manufacturer; a preferred coating is TiCN. The use of three flutes is
preferred for creation of a smoother surface, but the number of flutes is
not by itself a critical parameter. The preferred rotation speed is 1200
rpm. The right-handed orientation, coupled with counter-clockwise
rotation (as observed looking at the tip of the device, as illustrated by
the curved arrow in FIG. 2) means that the cutting edges advance into the
workpiece in the same direction as the advancing hood, i.e., the positive
X-direction. It is possible, but not necessary, to continue rotation of
the end mill as hood 15 is withdrawn (in the -X direction) so that the
rapidly spinning cutting surfaces smooth out the surface of combination
13 to ensure greater accuracy.

[0013]The cutting length of cutting subsystem 14 should be greater than
the width of part/potting combination 13 to ensure that the entire width
of part/potting combination 13 is cut in a single pass. The position of
cutting subsystem 14 with respect to the location of part/potting
combination 13 is coordinated accordingly.

[0014]Hood 15 enables conventional vacuum system 16 to quickly and
efficiently remove debris 18 from chamber 17 as such debris is created by
cutting subsystem 14 when it removes the layer of part/potting
combination 13. The exact shape of hood 15 is not critical. The function
of hood 15 is to concentrate the vacuum and keep the debris within a
contained volume. In the embodiment illustrated, hood 15 substantially
surrounds cutting subsystem 14 but for a relatively small open throat
facing the upper surface of the part/potting combination, through which
debris will be collected by the vacuum (see especially FIG. 3).

[0015]As with the cutting length of cutting subsystem 14, the width of
hood 15 (measured in the Y-direction) is greater than the width of
part/potting combination 13 to ensure that the entire width is cut in a
single pass. Hood 15 is mechanically attached or otherwise coordinated
with the position of cutting subsystem 14 so that both advance together
(in the X-direction) across the face of part/potting combination 13 to
remove the surface layer of material (thus generating the debris).

[0016]Any debris 18 generated by such removal is withdrawn through vacuum
hood 15, which is attached to conventional vacuum system 16. As
illustrated in this embodiment, system 10 further comprises a working
chamber 17, which is optional in the sense that system 10 could be
incorporated as a sub-system of a larger system if so desired.

[0017]Thus, the amount of motion required of the various components of
system 10 is substantially reduced compared to prior commercial
embodiments. To summarize, focal plane F remains fixed at all times;
table 11 (and thus part/potting combination 13) moves only in the Z
direction and not at all in the X or Y directions; hood/vacuum system 15,
16 moves only in the +/-X directions and not in the Y or Z directions;
and cutting subsystem 14 (in the preferred embodiment illustrated)
comprises a rotating end mill, having an axis of symmetry located such
that it is coordinated with the Z position of the part/potting
combination 13 to thereby remove only the necessary and desired amount of
material as that axis moves in only the +/-X direction and not the Y or Z
directions. The substantial reduction in the amount of moving
subassemblies enables a substantial reduction in the overall size of the
system 10, because it reduces overall structural, mechanical, and
electrical supporting equipment. This makes the system 10 highly suitable
for use with small part/potting combinations 13 such as those having the
non-limiting dimensions given above.

[0018]The techniques described above may be contrasted to the disclosure
of the patents listed above, which specifically disclose the use of
separate, dedicated locations for the material removal station and the
scanning station, such stations being separated from each other along the
so-called X axis. The time required to shuttle the stage bearing the
part/potting combination back and forth between these physically separate
stations reduces the cycle time of the entire process compared to the
approach disclosed above. By contrast, very low cycle times of
approximately 8-10 seconds are believed possible in commercial production
of the approach described above.

[0019]It is well known to use computers to control the operation and
location of the system as well as to process the data generated by the
scanning subsystem. The preferred, but not required, technique to convert
the scanning data is disclosed in the patents incorporated by reference
above, as well as U.S. Pat. No. 6,407,735, which is also incorporated by
reference.

Application to Cross-Sectional Scanning Systems

[0020]The techniques described above may be employed in a cross-sectional
scanning system of the following general design. Details of particular
embodiments of such systems are in the patents incorporated by reference
above.

[0021]The system produces electronic data representations of an object or
part. The major components of the system are: (1) a data gathering
station having a focal plane, the position of the focal plane being fixed
relative to the surface of the part; (2) a material removal station that
moves into and out of position over the surface of the part; and (3) a
table providing only vertical relative movement of the part to put the
surface at the position of the focal plane. The data gathering station
typically, but not necessarily, comprises: (1) an image data acquisition
device for successively acquiring images of the part after removal of a
predetermined contour; and (2) an electronic device operatively
associated with the image data acquisition device for receiving and
storing the images. The material removal station typically, but not
necessarily, comprises: (1) a tool constructed and arranged to remove a
predetermined contour of material from the part; and (2) a drive
mechanism constructed and arranged to provide relative movement between
the tool and the part. The table holds the part and is moved by a drive
mechanism constructed and arranged to provide only vertical relative
movement of the table; and a means to determine the relative locations of
the part and the focal plane along the vertical direction.

[0022]The operation of a typical configuration of such a system is as
follows. The image data acquisition device successively acquires images
of the part after removal of a predetermined contour. The tool is moved
into and out of relative material removing engagement with the part. The
relative movement between the table and the tool along the path is such
that the part and the tool are moved in material removal alignment for
removing a predetermined contour of material from the part and in imaging
alignment to the image data acquisition device after removal of a
predetermined contour. The position determining apparatus actuates the
image data acquisition device at predetermined positions of the part
relative to the tool. For example, a linear encoder with a scale, a
sensor, and a computer may be arranged to send signals to the computer in
response to the relative movement between the sensor and the scale. The
computer is programmed to determine the position of the scale relative to
the sensor in response to the signals received from the sensor. Thus,
because the scale and sensor are operatively associated with each other,
the position of the part relative to the tool along the path is
incrementally determined by the computer.

[0023]Commercial embodiments of such systems employ visible light (400-700
nm wavelength) for illumination and scanners sensitive to light typically
having a wavelength centered on 550 nm. However, such values are not
critical provided that sufficient contrast is provided at the detection
wavelength chosen. Similarly, while directly impinging illumination and
scanning normal to the surface have been illustrated, as is commercially
common, more complicated geometries are possible but not preferred.

[0024]While the above description refers to many specific details for the
sake of explanation, these details should not be construed as limitations
unless explicitly included in the following claims.